Quoted from tamoore:
Stern sends pinball machines all over the world, with the appropriate coin mechs installed. It can be done, and can't be that hard to orchestrate.
That means there has to be a reason other than "it's too hard"...
Making a pinball machine is hard. Accepting a coin? Not too much.
And really all they have to do is just ship them seperately. That would not require any expensive line retooling and it would not affect production.